In recent years, services based on AR (Augmented Reality) technology have been developed and provided. For example, a technique is known in which an object arranged around the location of a mobile terminal is acquired, and the object including a variety of information and images is overlaid and displayed on an image in real space acquired by a camera provided to the mobile terminal. Another technique is also known in which a predetermined marker is detected from an image in real space acquired by a camera in a mobile terminal, and an object associated with the marker is overlaid on the image in real space and displayed on a display. In addition, a device is known which generates an image of a marker with the color, brightness, contrast, resolution, and focus being changed from a registered image of the marker and detects the marker based on the generated image in order to detect markers well from images captured in various conditions (see, for example, Patent Literature 1). In a technique of detecting a marker by performing binarization processing on the captured image in real space, a device is known which attempts to detect a marker with a threshold for binarization being changed when a marker fails to be detected (see, for example, Patent Literature 2).